HOUSTON, Texas, Aug 27 (Reuters) - Emergency crews raced to pull people from cars and homes as flood waters rose across southeast Texas on Sunday, rescuing more than 1,000 people around Houston as Tropical Storm Harvey pounded the region.

Harvey came ashore late Friday as the most powerful hurricane to hit Texas in more than 50 years and has killed at least two people. The death toll is expected to rise as the storm lashes the U.S. state for days, triggering more floods, tidal surges and tornadoes.

Harvey has caused chest-deep flooding on some streets in Houston as rivers and channels overflow their banks. After up to 30 inches (76 cms) of rain in some parts of the fourth most-populous U.S. city, the storm is expected to dump 12 to 25 more inches (30-63 cms) over the next few days, the National Weather Service forecast. The total could reach 50 inches in some coastal areas of Texas by the end of the week, or the average rainfall for an entire year.

"This event is unprecedented and all impacts are unknown and beyond anything experienced," the government's National Weather Service said on Twitter. The center of Harvey is still 125 miles away from Houston, and forecast to arc slowly toward the city through Wednesday.

Flooding closed many roads and residents hunkered down inside houses and apartments as authorities sent flash flood and tornado alerts to cell phones.

The swift rise of flood waters surprised authorities and residents with boats were asked to help with rescues.

The Ben Taub Hospital in Houston's Medical Center was being evacuated on Sunday. An American Red Cross emergency shelter was forced to shut due to flooding and the group opened two more, including one in a convention center in downtown Houston.

"Within less than a half hour, we had 7 to 8 inches of water in our first floor," said Brian Hoskins, 25, a petroleum engineer who lives in Houston.

"I was worried about losing all our furniture and our cars."

Emergency services told people to climb onto the roofs of their houses rather than into their attics to escape rapidly rising waters, to avoid being trapped if waters rose more.

Authorities warned the city's more than two million residents and people across Texas not to leave homes even if they flooded because roads were impassable.

Many people were stuck in vehicles on raised highway sections with dips in the roads ahead of them flooded.

The Twitter account of the sheriff of Harris County, which includes most of Houston, was inundated with rescue requests and his team were unable to respond quickly to all of them.

Gonzalez said his deputies responded to unconfirmed reports of a deceased woman and child inside a submerged vehicle on a highway near Houston.

Another resident described seeing a woman's body floating in the streets during a flash flood in west Houston. The flood was several feet high, the resident told local TV station abc13.

Houston's Bush International and William P. Hobby airports canceled all commercial flights on Sunday. Hobby had standing water on the runway and said the arrivals area was flooded.

"The flooding in Houston is dramatic," Texas Governor Greg Abbott said in an interview on Fox News on Sunday.

The second confirmed fatality from Tropical Storm Harvey came on Saturday evening when an elderly woman drowned attempting to drive through flooded streets in west Houston, said city police Sergeant Colin Howard.

Authorities evacuated flooded apartment complexes and warned residents to heed warnings not to leave flooded residencies unless asked to do so as up to 5 inches (12.7 cm) of rain fell per hour.

"There are a number of stranded people on our streets, calling 911, exhausting needed resources. You can help by staying off the streets," Houston Mayor Sylvester Turner said on Twitter.

On Friday night, a man died in a house fire in the town of Rockport, 30 miles (48 km) north of the city of Corpus Christi. Another dozen people in the area suffered injuries including broken bones, another official said.

Harvey struck at the heart of the country's oil and gas industry, forcing operators to close several refineries to close and evacuate offshore platforms.

Millions of barrels per day of fuel production have been halted, and gasoline prices rose ahead of the storm. Benchmark gasoline futures were likely to rise again as shutdowns extended from to the refining hub of Houston. Refiners further south in the area around Corpus Christi had already shut.

Exxon Mobil said Sunday it was closing the second largest refinery in the United States at Baytown in Texas.

More than 45 percent of the country's refining capacity is along the U.S. Gulf Coast, and nearly a fifth of the nation's crude oil is produced offshore in the Gulf of Mexico.

Abbott said Sunday he expected disruption to the energy industry to last one or two weeks.

HARVEY THREATENS RECORD RAIN

Harvey slammed into Texas as a Category 4 hurricane with winds of 130 miles per hour (210 km per hour), making it the strongest storm to hit the state since 1961.

The storm ripped off roofs, destroyed buildings, flooded coastal towns and had cut off power to nearly 230,000 people in Texas as of Saturday night.

Harvey was downgraded to a tropical storm on Saturday because its winds have slowed. But authorities issued stark warnings on the threat posed by days of torrential rain.

"This rain will lead to a prolonged, dangerous, and potentially catastrophic flooding event well into next week," the National Weather Service said in a statement.

Harvey threatens to break the record established nearly 40 years ago when Alvin, Texas, was deluged by 43 inches of rain in 24 hours on July 24-25, 1979.

'IT WAS TERRIBLE'

Abbott said 1,800 members of the military would help with the statewide cleanup. Another 1,000 people were conduct search-and-rescue operations.

The coastal town of Rockport took a direct hit from the storm, leaving streets flooded and strewn with power lines and debris on Saturday.

A convoy of military vehicles arrived in the Rockport area on Saturday to help in the recovery efforts, and town officials announced an overnight curfew for residents. The Texas Department of Criminal Justice said it was forced to evacuate about 4,500 inmates from three state prisons near the Brazos River because of rising water. The U.S. Coast Guard said it had rescued 20 people from distressed vessels on Saturday, and was monitoring two Carnival Corp cruise ships carrying thousands of people stranded in the U.S. Gulf of Mexico.

The size and strength of Harvey dredged up memories of Katrina, the 2005 hurricane that made a direct hit on New Orleans as a Category 3 storm, causing levees and flood walls to fail in dozens of places. About 1,800 died in the disaster made worse by a slow government emergency response.

U.S. President Donald Trump, facing the first big natural disaster of his term, said on Sunday he would visit the area as soon as he could do so without causing more disruption.

He said the all-out effort to deal with the disaster was going well. Trump signed a disaster proclamation on Friday, triggering federal relief efforts.

Heavy cloud cover across most of the state was making helicopter relief supply deliveries difficult, the White House's Homeland Security Advisor, Tom Bossert, said on CBS Face the Nation.

Recovery would likely take years, the administrator of the Federal Emergency Management Agency (FEMA) Brock Long said in an interview with CNN on Sunday. FEMA coordinates the response to major disasters.